Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

The purpose of the present invention is to make a change in the
chromaticity of an optical member due to use unlikely to occur. A method
of manufacturing a prism sheet 23c as an optical member 23 to be used in
a backlight unit 12 that supplies light to a liquid crystal panel 11 and
transmits light from LEDs 24 as light sources of the backlight unit 12,
includes a step of stabilizing the chromaticity of transmitted light by
irradiation with light from chromaticity stabilizing LEDs 32 as
chromaticity stabilizing light sources having a dominant emission
wavelength in a blue wavelength region.

Claims:

1. A method of manufacturing an optical member to be used in a lighting
device supplying light to a display panel and transmitting light from a
light source included in the lighting device, the method comprising:
stabilizing chromaticity of light transmitted through the optical member
by irradiation with light having a dominant emission wavelength in a blue
wavelength region that is emitted from a chromaticity stabilizing light
source.

2. The method of manufacturing an optical member according to claim 1,
wherein in the chromaticity stabilizing step, the light having the
dominant emission wavelength in the blue wavelength region that is
emitted from the chromaticity stabilizing light source has an emission
intensity relatively higher than an emission intensity of a light source
included in the lighting device.

3. The method of manufacturing an optical member according to claim 2,
wherein in the chromaticity stabilizing step, the dominant emission
wavelength of the chromaticity stabilizing light source is same as a
dominant emission wavelength of the light source included in the lighting
device.

4. The method of manufacturing an optical member according to claim 1,
wherein in the chromaticity stabilizing step, the chromaticity
stabilizing light source emits substantially single color light of blue.

5. The method of manufacturing an optical member according to claim 4,
wherein in the chromaticity stabilizing step, the chromaticity
stabilizing light source is a chromaticity stabilizing LED having a LED
element emitting the substantially single color light of blue.

6. The method of manufacturing an optical member according to claim 1,
further comprising forming a light transmissive base member of the
optical member, wherein in the chromaticity stabilizing step, at least
the light transmissive base member is irradiated with the light from the
chromaticity stabilizing light source.

7. The method of manufacturing an optical member according to claim 6,
wherein in the base member forming step, the light transmissive base
member is formed from a polyester resin.

8. The method of manufacturing an optical member according to claim 7,
wherein in the base member forming step, the light transmissive base
member is formed from PET (polyethylene terephthalate).

9. The method of manufacturing an optical member according to claim 6,
wherein in the base member forming step, the light transmissive base
member is formed from an AS resin (acrylonitrile-styrene copolymer).

10. The method of manufacturing an optical member according to claim 6,
further comprising forming an optical functional layer on the light
transmissive base member, the optical functional layer optically
affecting the light from the light source of the lighting device.

11. The method of manufacturing an optical member according to claim 10,
wherein the chromaticity stabilizing step is performed after the base
member forming step and the functional layer forming step.

12. The method of manufacturing an optical member according to claim 11,
wherein in the chromaticity stabilizing step, the chromaticity
stabilizing light source is disposed to face at least the light
transmissive base member.

13. The method of manufacturing an optical member according to claim 12,
wherein in the chromaticity stabilizing step, the chromaticity
stabilizing light source is disposed to face the light transmissive base
member among the light transmissive base member and the optical
functional layer.

14. The method of manufacturing an optical member according to claim 10,
wherein the optical functional layer is a prism layer that collects the
light from the light source of the lighting device.

15. The method of manufacturing an optical member according to claim 14,
wherein the prism layer is made of a non-halogenated acrylic resin.

16. The method of manufacturing an optical member according to claim 10,
wherein the optical functional layer is a diffuser layer diffusing light
from the light source of the lighting device.

17. The method of manufacturing an optical member according to claim 16,
wherein the diffuser layer is made of an alkyl methacrylate styrene
non-copolymer.

18. The method of manufacturing an optical member according to claim 1,
wherein in the chromaticity stabilizing step, the light from the
chromaticity stabilizing light is irradiated to the optical member to be
used in the lighting device including the light source configured with a
LED having a LED element emitting substantially single color light of
blue and a phosphor emitting light upon excitation by the light from the
LED element.

19. The method of manufacturing an optical member according to claim 1,
wherein in the chromaticity stabilizing step, the light from the
chromaticity stabilizing light is irradiated to the optical member to be
used in the lighting device supplying light to the display panel
including a pair of substrates sandwiching a substance with optical
characteristics variable by application of an electric field, one of the
pair of substrates including a color filter with a plurality of color
sections respectively exhibiting blue, green, red, or yellow.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing an
optical member.

BACKGROUND ART

[0002] A liquid crystal panel used in a liquid crystal display device,
such as a liquid crystal television set, does not emit light by itself.
Thus, the liquid crystal panel uses a backlight unit as a separate
lighting device. The backlight unit is installed on the rear side
(opposite to the display surface) of the liquid crystal panel, and
provided with a chassis with an opening on the liquid crystal panel side;
a light source housed in the chassis; and optical members disposed in the
opening of the chassis in an opposed manner with respect to the light
source and converting the light from light source into planar light to
output the light toward the liquid crystal panel, for example.

[0003] The optical members of the backlight unit causes the light from the
light source to be output toward the liquid crystal panel while providing
the light with a predetermined optical effect based on the type of the
optical members. For example, a prism sheet collects light from the light
source, and a diffuser sheet diffuses light from the light source. An
example of the backlight unit including such optical members is described
in the following Patent Document 1.

[0005] The optical characteristics of the optical members may be varied by
use, depending on the type of material of the constituent parts of the
optical members or the environment in which the backlight unit is used.
As a result, the chromaticity of the transmitted light may be shifted
over time. When there is such a chromaticity shift in the light
transmitted through the optical members, a tinge of color of the image
displayed on the liquid crystal display device may be gradually changed
over time of use, possibly resulting in a decrease in display quality.
This problem of chromaticity shift in the transmitted light through the
optical members has not been sufficiently analyzed.

DISCLOSURE OF THE PRESENT INVENTION

[0006] The present invention was made in view of the foregoing
circumstances, and an object of the present invention is to make a change
in chromaticity due to use unlikely to occur.

Means for Solving the Problem

[0007] According to the present invention, a method of manufacturing an
optical member to be used in a lighting device supplying light to a
display panel and transmitting light from a light source included in the
lighting device, includes stabilizing chromaticity of light transmitted
through the optical member by irradiation with light having a dominant
emission wavelength in a blue wavelength region that is emitted from a
chromaticity stabilizing light source.

[0008] If the optical member is manufactured without the chromaticity
stabilizing step, if the manufactured optical member is assembled and
used in the lighting device irradiating the display panel with light, the
optical characteristics of the optical member may be changed such that
the chromaticity of the color of white of the transmitted light is
gradually shifted toward blue as the optical member is irradiated with
the light in the blue wavelength region from the light source of the
lighting device. As a result, a tinge of color of the displayed image may
be changed over time, possibly resulting in decrease in display quality,
for example.

[0009] According to the present invention, when the optical member is
manufactured, in the chromaticity stabilizing step, the optical
characteristics of the optical member is changed by irradiation with the
light having the dominant emission wavelength in the blue wavelength
region from the chromaticity stabilizing light source such that the
chromaticity of the transmitted light through the optical member can be
shifted toward blue. Namely, a change in the optical characteristics of
the optical member used in the lighting device is promoted during the
manufacturing process such that the chromaticity of the color of white of
the transmitted light is shifted toward blue in advance, whereby the
chromaticity of the transmitted light can be stabilized. Thus, a change
in the chromaticity is unlikely to occur when the optical member is
assembled and used in the lighting device. Accordingly, when the optical
member is used in the lighting device, the tinge of color of the
displayed image on the display panel is not changed over time, leading to
excellent display quality. In addition, because the light from the
chromaticity stabilizing light source has the dominant emission
wavelength in the blue wavelength region, the change in the optical
characteristics of the optical member can be efficiently promoted,
whereby time required for the chromaticity stabilizing step can be
decreased, providing excellent manufacturing efficiency.

[0010] Preferred embodiments of the present invention may include the
following.

[0011] (1) In the chromaticity stabilizing step, the light having the
dominant emission wavelength in the blue wavelength region that is
emitted from the chromaticity stabilizing light source may have an
emission intensity relatively higher than an emission intensity of a
light source included in the lighting device. In this way, the optical
irradiation time necessary for stabilizing the chromaticity of the
transmitted light through the optical member in the chromaticity
stabilizing step can be decreased as the emission intensity of the light
in the blue wavelength region is increased. Thus, time required for the
chromaticity stabilizing step can be decreased compared with the case
where the same light source of the lighting device is used as the
chromaticity stabilizing light source.

[0012] (2) In the chromaticity stabilizing step, the dominant emission
wavelength of the chromaticity stabilizing light source may be same as a
dominant emission wavelength of the light source included in the lighting
device. In this way, the optical characteristics of the optical member
can be more appropriately changed in the chromaticity stabilizing step.
Thus, when the manufactured optical member is assembled and used in the
lighting device, the tinge of color of the displayed image on the display
panel can be more appropriate. Accordingly, extremely high display
quality can be obtained.

[0013] (3) In the chromaticity stabilizing step, the chromaticity
stabilizing light source may emit substantially single color light of
blue. In this way, the optical member can be irradiated with the light in
the blue wavelength region in an extremely efficient manner in the
chromaticity stabilizing step. As a result, the optical irradiation time
necessary for stabilizing the chromaticity of the transmitted light
through the optical member can be decreased in the chromaticity
stabilizing step. Thus, time required for the chromaticity stabilizing
step can be further decreased.

[0014] (4) In the chromaticity stabilizing step, the chromaticity
stabilizing light source may be a chromaticity stabilizing LED having a
LED element emitting the substantially single color light of blue. In
this way, the optical member can be irradiated with the substantially
single color light of blue with extremely high color purity from the LED
element of the chromaticity stabilizing LED in the chromaticity
stabilizing step. Thus, the time required for the chromaticity
stabilizing step can be further decreased.

[0015] (5) The method of manufacturing an optical member may further
include forming a light transmissive base member of the optical member.
In the chromaticity stabilizing step, at least the light transmissive
base member may be irradiated with the light from the chromaticity
stabilizing light source. This may be suitable in the case where a change
in the optical characteristics of the optical member is caused due to the
light transmissive base member.

[0016] (6) In the base member forming step, the light transmissive base
member may be formed from a polyester resin. In this way, the
chromaticity of the transmitted light through the light transmissive base
member of the polyester resin can be stabilized through the chromaticity
stabilizing step.

[0017] (7) In the base member forming step, the light transmissive base
member may be formed from PET (polyethylene terephthalate). In this way,
while PET includes a carbonyl group as the chromophore and the carbonyl
group may be a factor causing a change in the optical characteristics,
the chromaticity of the transmitted light through the light transmissive
base member of PET can be stabilized through the chromaticity stabilizing
step.

[0018] (8) In the base member forming step, the light transmissive base
member may be formed from an AS resin (acrylonitrile-styrene copolymer).
In this way, the chromaticity of the transmitted light through the light
transmissive base member of the AS resin can be stabilized through the
chromaticity stabilizing step.

[0019] (9) The method of manufacturing an optical member may further
include forming an optical functional layer on the light transmissive
base member. The optical functional layer optically affects the light
from the light source of the lighting device. In this way, the optical
member formed by layering the optical functional layer on the light
transmissive base member can be manufactured in a preferred manner.

[0020] (10) The chromaticity stabilizing step may be performed after the
base member forming step and the functional layer forming step. If the
base member forming step and the functional layer forming step are
performed successively, performing the chromaticity stabilizing step
prior to the functional layer forming step would require a significant
modification of the manufacturing apparatus. In this respect, according
to the present invention, the chromaticity stabilizing step can be
included in the method of manufacturing the optical member without a
significant modification of the manufacturing apparatus.

[0021] (11) In the chromaticity stabilizing step, the chromaticity
stabilizing light source may be disposed to face at least the light
transmissive base member. In this way, the light transmissive base member
can be irradiated with the light from the chromaticity stabilizing light
source efficiently in the chromaticity stabilizing step. Thus, the
stabilizing the chromaticity of the transmitted light through the light
transmissive base member can be performed in less time.

[0022] (12) In the chromaticity stabilizing step, the chromaticity
stabilizing light source may be disposed to face the light transmissive
base member among the light transmissive base member and the optical
functional layer. In this way, because the chromaticity stabilizing light
source is disposed to face only one side of the optical member, the cost
related to the optical member manufacturing apparatus can be decreased
compared with the case where the chromaticity stabilizing light source is
disposed to face both sides of the optical member.

[0023] (13) The optical functional layer maybe a prism layer that collects
the light from the light source of the lighting device. In this case,
because the prism layer collects the light transmitting through the
optical member, the chromaticity shift of the color of white of the
transmitted light toward blue tends to become more conspicuous. In this
respect, according to the present invention, the chromaticity of the
transmitted light through the optical member is stabilized in advance in
the chromaticity stabilizing step. This is extremely useful for the
manufacture of the optical member including the prism layer.

[0024] (14) The prism layer may be made of a non-halogenated acrylic
resin. In this way, the optical member including the prism layer of the
non-halogenated acrylic resin can be manufactured in an extremely useful
manner.

[0025] (15) The optical functional layer may be a diffuser layer diffusing
light from the light source of the lighting device. In this way, the
optical member including the diffuser layer that diffuses the transmitted
light can be manufactured in a preferred manner.

[0026] (16) The diffuser layer may be made of an alkyl methacrylate
styrene non-copolymer. In this way, the optical member including the
diffuser layer of the alkyl methacrylate styrene non-copolymer can be
manufactured in a preferred manner.

[0027] (17) In the chromaticity stabilizing step, the light from the
chromaticity stabilizing light is irradiated to the optical member to be
used in the lighting device including the light source configured with a
LED having a LED element emitting substantially single color light of
blue and a phosphor emitting light upon excitation by the light from the
LED element. If the optical member is used in the lighting device having
the LED as the light source, the problem of the chromaticity shift of the
transmitted light due to a change in the optical characteristics of the
optical member may become pronounced because of the substantially single
color light of blue with extremely high color purity from the LED
element. By stabilizing the chromaticity of the transmitted light through
the optical member to be used in such lighting device in the chromaticity
stabilizing step, the problem of chromaticity shift can be eliminated in
a preferred manner.

[0028] (18) In the chromaticity stabilizing step, the light from the
chromaticity stabilizing light is irradiated to the optical member used
in the lighting device supplying light to the display panel including a
pair of substrates sandwiching a substance with optical characteristics
variable by application of an electric field, one of the pair of
substrates including a color filter with a plurality of color sections
respectively exhibiting blue, green, red, and yellow. Because the color
filter included in the display panel includes the yellow color section in
addition to the respective blue, green, and red color sections, the
displayed image on the display panel tends to have a yellowish tinge. In
order to avoid this, it is preferable to set the chromaticity of the
output light from the light source of the lighting device toward blue
that is the complementary color to yellow. However, in this case, the
problem of the chromaticity shift of the transmitted light in the optical
member may become pronounced as the lighting device is used. The problem
of chromaticity shift can be eliminated in a preferred manner by
stabilizing the chromaticity of the transmitted light with respect to the
optical member to be used in the lighting device supplying light to the
display panel in the chromaticity stabilizing step.

Advantageous Effect of the Invention

[0029] According to the present invention, a change in chromaticity due to
use can be made difficult to occur.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a an exploded perspective view illustrating a schematic
configuration of a television receiver according to the first embodiment
of the present invention;

[0031]FIG. 2 is an exploded perspective view showing a schematic
configuration of a liquid crystal display device included in the
television receiver;

[0032]FIG. 3 is a cross sectional view showing a cross sectional
configuration of a liquid crystal panel along a long side direction
thereof;

[0033] FIG. 4 is an enlarged plan view illustrating a planar configuration
of an array substrate;

[0034]FIG. 5 is an enlarged plan view illustrating a planar configuration
of a CF substrate;

[0035] FIG. 6 is a plan view showing an arrangement configuration of
diffuser lenses, LED boards, first reflection sheets and holding members
in a chassis of a backlight unit;

[0036] FIG. 7 is a cross sectional view of the liquid crystal display
device taken along line vii-vii of FIG. 6;

[0037]FIG. 8 is a cross sectional view of the liquid crystal display
device taken along line viii-viii of FIG. 6;

[0038] FIG. 9 is a graph showing the relationship between the duration of
time that a prism sheet has been irradiated with the light from LEDs of
the backlight unit and the chromaticity of the color of white of the
transmitted light through the prism sheet;

[0039] FIG. 10 is a CIE1931 chromaticity diagram showing the chromaticity
coordinates of the color of white of the transmitted light through the
prism sheet before irradiation on the prism sheet with the light from the
LEDs of the backlight unit and after irradiation for 100 hours;

[0040]FIG. 11 is a graph showing the relationship between the wavelength
of the transmitted light through the prism sheet and the transmittance of
the transmitted light;

[0041]FIG. 12 is a schematic perspective view illustrating a step of
forming a base member and a step of forming a prism layer included in a
method of manufacturing the prism sheet;

[0042] FIG. 13 is a schematic perspective view illustrating a step of
stabilizing chromaticity included in the method of manufacturing the
prism sheet;

[0043] FIG. 14 is a schematic perspective view illustrating a step of
forming a base member and a step of forming a diffuser layer included in
a method of manufacturing a diffuser sheet according to a second
embodiment of the present invention;

[0044] FIG. 15 is a schematic perspective view illustrating a step of
stabilizing chromaticity included in the method of manufacturing the
diffuser sheet;

[0045] FIG. 16 is an exploded perspective view of a liquid crystal display
device including an edge light backlight unit according to a third
embodiment of the present invention;

[0046] FIG. 17 is a cross sectional view showing a cross sectional
configuration of the liquid crystal display device of FIG. 16, along a
short side direction thereof;

[0047] FIG. 18 is a cross sectional view showing a cross sectional
configuration of the liquid crystal display device of FIG. 16, along a
long side direction thereof;

[0049] FIG. 20 is an enlarged plan view showing a planar configuration of
a CF substrate according to a fourth embodiment of the present invention;

[0050] FIG. 21 is a cross sectional view showing a cross sectional
configuration of a liquid crystal panel including the CF substrate of
FIG. 20 along a long side direction;

[0051]FIG. 22 is an enlarged plan view showing a planar configuration of
a CF substrate according to another embodiment (1) of the present
invention; and

[0052]FIG. 23 is an enlarged plan view showing a planar configuration of
a CF substrate according to another embodiment (2) of the present
invention.

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

[0053] A first embodiment of the present invention will be described with
reference to FIGS. 1 to 13. According to the present embodiment, a method
of manufacturing an optical member 23 (a prism sheet 23c) to be used in a
liquid crystal display device 10 will be described. In the following, a
configuration of the liquid crystal display device 10 will be described
first. In some parts of the drawings, an X-axis, a Y-axis, and a Z-axis
are shown as the respective axial directions corresponding to the
directions shown in the respective drawings. The upper side and the lower
side shown in FIGS. 7 and 8 correspond to the front side and the rear
side, respectively.

[0054] A television receiver TV according to the present embodiment, as
shown in FIG. 1, includes the liquid crystal display device 10; front and
rear cabinets Ca and Cb housing the liquid crystal display device 10 in a
sandwiching manner; a power supply circuit board P supplying electric
power; a tuner (reception unit) T configured to receive a television
image signal; an image conversion circuit board VC converting the
television image signal output from the tuner T into an image signal for
the liquid crystal display device 10; and a stand S. The liquid crystal
display device (display device) 10 as a whole has a horizontally long
(elongated) square shape (rectangular shape). The liquid crystal display
device 10 is housed with its long side direction and short side direction
substantially aligned with the horizontal direction (X-axis direction)
and the vertical direction (Y-axis direction; perpendicular direction),
respectively. The liquid crystal display device 10, as shown in FIG. 2,
includes a liquid crystal panel 11 as a display panel and a backlight
unit (lighting device) 12 as an external light source, which are
integrally held by a frame-shaped bezel 13 or the like.

[0055] A configuration of the liquid crystal panel 11 of the liquid
crystal display device 10 will be described in detail. The liquid crystal
panel 11 as a whole has a horizontally long (elongated) square shape
(rectangular shape). As shown in FIG. 3, the liquid crystal panel 11
includes a pair of transparent (light transmissive) glass substrates 11a
and 11b, and a liquid crystal layer 11c between the substrates 11a and
11b. The liquid crystal layer 11c includes liquid crystal. The liquid
crystal is a substance whose optical characteristics vary by application
of an electric field. The substrates 11a and 11b are affixed to each
other with a sealing agent, which is not shown, with a gap corresponding
to the thickness of liquid crystal layer 11c maintained between the
substrates 11a and 11b. To the outer surfaces of the substrates 11a and
11b, polarizing plates 11d and 11e, respectively, are affixed. The liquid
crystal panel 11 has a long side direction and a short side direction
aligned with the X-axis direction and the Y-axis direction, respectively.

[0056] The front side (front surface side) one of the substrates 11a and
11b is a CF substrate 11a, and the rear side (back surface side) one of
the substrates 11a and 11b is an array substrate 11b. On an inner surface
of the array substrate 11b, i.e., the surface facing the liquid crystal
layer 11c (facing the CF substrate 11a), as shown in FIG. 4, a number of
TFTs (Thin Film Transistors) 14 and pixel electrodes 15 as switching
elements are arranged side by side in a matrix. Around the TFTs 14 and
the pixel electrodes 15, gate wires 16 and source wires 17 are arranged
in a lattice shape. The pixel electrodes 15 have a vertically long
(elongated) square shape (rectangular shape) with a long side direction
and a short side direction aligned with the Y-axis direction and the
X-axis direction, respectively. The pixel electrodes 15 may be
transparent electrodes of ITO (Indium Tin Oxide) or ZnO (Zinc Oxide). The
gate wires 16 and the source wires 17 are connected to the gate
electrodes and the source electrodes of the TFTs 14, respectively. The
pixel electrodes 15 are connected to the drain electrodes of the TFTs 14.
On the side of the TFTs 14 and the pixel electrodes 15 facing the liquid
crystal layer 11c, an alignment film 18 aligning the liquid crystal
molecules is arranged. At the ends of the array substrate 11b, terminal
portions drawn out from the gate wires 16 and the source wires 17 are
formed. To the terminal portions, a driver IC, which is not shown,
driving the liquid crystal is crimped via an anisotropic conductive film
(ACF). The liquid crystal driving driver IC is electrically connected to
a display control circuit board, which is not shown, via various wiring
boards and the like. The display control circuit board is connected to
the image conversion circuit board VC of the television receiver TV to
supply a drive signal via the driver IC to the wires 16 and 17 on the
basis of an output signal from the image conversion circuit board VC.

[0057] On the inner surface of the CF substrate 11a, i.e., on the surface
facing the liquid crystal layer 11c (or facing the array substrate 11b),
as shown in FIGS. 3 and 5, a color filter 19 is arranged. The color
filter 19 includes a plurality of each of color sections R, G, B, or Y
arranged in a matrix corresponding to the respective pixels on the array
substrate 11b. According to the present embodiment, the color filter 19
includes a yellow color section Y in addition to the red color section R,
the green color section G, and the blue color section B of the three
primary colors of light. The respective color sections R, G, B, and Y
selectively transmit light of the respective corresponding colors
(respective wavelengths). In the color filter 19, the red color section
R, the green color section G, the yellow color section Y, and the blue
color section B are arranged along the x-axis direction in the order from
the left side as shown in FIG. 5. The color sections R, G, B, and Y have
a vertically long (elongated) square shape (rectangular shape) with a
long side direction aligned with the Y-axis direction and a short side
direction aligned with the X-axis direction, similar to the pixel
electrodes 15. All the color sections have the same area. Between the
color sections R, G, B, and Y, a lattice-shaped light blocking layer
(black matrix) BM is provided for preventing the mixing of colors. On the
side of the color filter 19 on the CF substrate 11a facing the liquid
crystal layer 11c, a counter electrode 20 and an alignment film 21 are
layered in order.

[0058] Thus, according to the present embodiment, the liquid crystal
display device 10 has the liquid crystal panel 11 with the color filter
19 including the four color sections R, G, B, and Y. For this reason, the
television receiver TV includes the dedicated image conversion circuit
board VC. The image conversion circuit board VC is configured to convert
the television image signal output from the tuner T into an image signal
for the respective colors of blue, green, red, or yellow to output the
image signal generated for the respective colors to the display control
circuit board. On the basis of the image signals, the display control
circuit board drives the TFTs 14 corresponding to the pixel of the
respective colors on the liquid crystal panel 11 to appropriately control
the amount of light transmitted through the color section R, G, B, or Y
of the respective colors.

[0059] Next, a configuration of the backlight unit 12 will be described.
The backlight unit 12, as shown in FIG. 2, includes a substantially
box-shaped chassis 22 with an opening on the light output surface side
(toward the liquid crystal panel 11); a group of optical members 23
covering the opening of the chassis 22; and a frame 26 arranged along the
outer edges of the chassis 22 and retaining the outer edges of the group
of optical members 23 in a sandwiched manner with the chassis 22. The
chassis 22 houses LEDs 24 arranged immediately under the optical members
23 (the liquid crystal panel 11) in an opposed manner; LED boards 25 on
which the LEDs 24 are mounted; and diffuser lenses 27 attached to the LED
boards 25 at positions corresponding to the LEDs 24. Thus, the backlight
unit 12 according to the present embodiment is of the so-called direct
type. The chassis 22 also houses holding members 28 configured to hold
the LED boards 25 between with the chassis 22; and a reflection sheet 29
reflecting the light within the chassis 22 toward the optical members 23.
In the following, the constituent components of the backlight unit 12
will be described in detail.

[0060] The chassis 22 is made of metal and, as shown in FIGS. 6 to 8,
includes a bottom plate 22a with a horizontally long square shape
(rectangular shape) similar to the liquid crystal panel 11; side plates
22b rising from the outer ends of the bottom plate 22a along the sides
thereof (a pair of long sides and a pair of short sides) toward the front
side (light output side); and backing plates 22c extending outward from
the rising ends of the side plates 22b. Thus, the chassis 22 as a whole
has a shallow box-like shape (substantially shallow dish-like shape) with
an opening on the front side. The chassis 22 has a long side direction
aligned with the X-axis direction (the horizontal direction) and a short
side direction aligned with the Y-axis direction (the vertical
direction). The backing plates 22c of the chassis 22 are configured to
receive the frame 26 and the optical members 23 from the front side, as
will be described later. The frame 26 is threadably mounted on the
backing plates 22c. The bottom plate 22a of the chassis 22 has attaching
holes 22d into which the holding members 28 are attached. Specifically, a
plurality of the attaching holes 22d is arranged in a distributed manner
correspondingly to the positions at which the holding members 28 are
attached on the bottom plate 22a.

[0061] The optical members 23, as shown in FIG. 2, have a horizontally
long square shape in plan view similar to the liquid crystal panel 11 and
the chassis 22. The optical members 23, as shown in FIGS. 7 and 8, are
arranged between the liquid crystal panel 11 and the LEDs 24 (LED boards
25) with the outer edges thereof received on the backing plates 22c to
cover the opening of the chassis 22. The optical members 23 include the
diffuser plate 23a on the rear side (facing the LEDs 24; opposite to the
light output side), and the optical sheets 23b, 23c on the front side
(facing the liquid crystal panel 11; the light output side). The diffuser
plate 23a includes a substantially transparent plate-like base substrate
of a resin with a predetermined thickness, in which a number of diffusing
particles are dispersed. The diffuser plate 23a has the function of
diffusing transmitted light. The optical sheets 23b, 23c are two sheets
layered, each with a thickness smaller than the one of the diffuser plate
23a. Specifically, the optical sheets 23b, 23c may include a diffuser
sheet, a prism sheet, and a reflection type polarizing sheet. According
to the present embodiment, the diffuser sheet 23b and the prism sheet
(lens sheet) 23c are used. These optical sheets 23b, 23c are layered on
the diffuser plate 23a in the order of the diffuser sheet 23b and the
prism sheet 23c from the back side. The diffuser sheet 23b has a
diffusing function of diffusing the transmitted light.

[0062] A configuration of the prism sheet 23c will be described in detail.
The prism sheet 23c, as shown in FIG. 12, includes a light transmissive
base member 30 with excellent transmissivity, and a prism layer (optical
functional layer) 31 layered on a main plate surface of the light
transmissive base member 30. The prism sheet 23c diffuses light
transmitting therethrough. The prism layer 31 is disposed on the front
side (the light output side; facing the liquid crystal panel 11) of the
light transmissive base member 30. Conversely, the light transmissive
base member 30 is disposed on the rear side (opposite to the light output
side; facing the LEDs 24) of the prism layer 31. The light transmissive
base member 30 is substantially transparent and has a horizontally long
sheet shape with a generally smooth surface. On the other hand, the prism
layer 31 includes a number of prisms 31a with substantially triangular
cross section, which are arranged in parallel with each other. The prisms
31a extend in parallel with one side of the light transmissive base
member 30. The parallel arrangement direction of the prisms 31a is
substantially orthogonal to the direction in which the prisms 31a extend.
The light transmitted through the prism sheet 23c may be refracted or
reflected, as appropriate, by the prisms 31a of the prism layer 31 such
that the light travels toward the front surface as much as possible. The
light transmissive base member 30 is made of a polyethylene resin, more
specifically a PET (Poly-Ethylene-Terephthalate). The prism layer 31 is
made of a non-halogenated acrylic resin. The prism sheet 23c may be
preferably a "BEF3", which is a trade name, manufactured by Sumitomo 3M
Limited. A detailed method of manufacturing the prism sheet 23c will be
described later.

[0063] The frame 26, as shown in FIG. 2, has a frame-like shape extending
along the outer peripheral edges of the liquid crystal panel 11 and the
optical members 23. The frame 26 is configured to sandwich the outer
edges of the optical members 23 (FIGS. 7 and 8) with the backing plates
22c. The frame 26 is also configured to receive the outer edges of the
liquid crystal panel 11 on the rear side to sandwich the outer edges of
the liquid crystal panel 11 with the bezel 13 on the front side (FIGS. 7
and 8).

[0064] Next, the LEDs 24 and the LED boards 25 will be described. The LEDs
24 are mounted on LED boards 25, and include the light emitting surface
on the opposite side of the mounting surface on LED boards 25 as shown in
FIGS. 6 to 8. That is, the LEDs 24 are of the top type. The LEDs 24
include a board portion which is fixedly attached on the LED boards 25.
On the board portion, LED chips (LED elements; light emitting elements)
of an InGaN based material, for example, are sealed on with a resin
material. The LED chips mounted on the board portion have a single peak
wavelength in the range of 435 nm to 480 nm, i.e., a blue wavelength
region, and emit the single color light of blue. More preferably, the LED
chips have a dominant emission wavelength in the range of 440 nm to 460
nm, such as 451 nm, for example. Thus, the LED chips emit the single
color light of blue with excellent color purity.

[0065] The resin material with which the LED chips are sealed contains the
green phosphor that emits green light upon excitation by the single color
of blue light emitted by the LED chips, and the red phosphor that emits
red light upon excitation by the single color of blue light emitted by
the LED chips, the green phosphor and the red phosphor being dispersed at
a predetermined ratio. On the basis of the blue light (light of blue
component) emitted by the LED chips, the green light (light of green
component) emitted from the green phosphor, and the red light (light of
red component) emitted from the red phosphor, the LEDs 24 as a whole are
configured to emit light of a predetermined color, such as white or
bluish white. The dominant emission wavelength of the light emitted by
the LEDs 24, i.e., the peak wavelength at which the emission intensity is
at the maximum, corresponds to the peak wavelength of the LED chips and
belongs to the blue wavelength region. By combining the light of green
component from the green phosphor and the light of red component from the
red phosphor, yellow light can be obtained. Thus, it can be said that the
LEDs 24 have the light of yellow component in addition to the light of
blue component from the LED chips.

[0066] The LED boards 25, as shown in FIGS. 6 and 7, include base members
with a horizontally long square shape in plan view. The LED boards 25 are
housed in the chassis 22 along the bottom plate 22a with a long side
direction aligned with the X-axis direction and a short side direction
aligned with the Y-axis direction. On the front side of the plate
surfaces of the base members of the LED boards 25 (i.e., facing the
optical members 23), the LEDs 24 are surface-mounted. The light emitting
surfaces of the LEDs 24 face the optical members 23 (the liquid crystal
panel 11) with an optical axis aligned with the Z-axis direction, which
is orthogonal to the display surface of the liquid crystal panel 11.
Specifically, a plurality of the LEDs 24 is arranged linearly side by
side along the long side direction (X-axis direction) of the LED boards
25, and connected in series by a wiring pattern formed on the LED boards
25. The LEDs 24 have a substantially constant arrangement pitch; namely,
the LEDs 24 are arranged at regular intervals. At the respective ends of
the LED boards 25 in the long side direction, connector portion 25a is
provided.

[0067] As shown in FIG. 6, a plurality of the LED boards 25 with the above
configuration is arranged side by side in the X-axis direction and the
Y-axis direction in the chassis 22, with their long side directions and
short side directions aligned with each other. Namely, the LED boards 25
and the LEDs 24 mounted thereon are arranged in rows and columns (in a
matrix or planar arrangement) in the chassis 22, the row direction
corresponding to the X-axis direction (the long side direction of the
chassis 22 and the LED boards 25) and the column direction corresponding
to the Y-axis direction (the short side direction of the chassis 22 and
the LED boards 25). Specifically, a total of 27 LED boards 25, i.e.,
three in the X-axis direction times nine in the Y-axis direction, are
arranged side by side in the chassis 22. The LED boards 25 arranged along
the X-axis direction to form a row are mutually electrically connected by
the adjacent connector portions 25a fitted to each other. The connector
portions 25a corresponding to the ends of the chassis 22 in the X-axis
direction are electrically connected to an external control circuit,
which is not shown. Thus, all of the LEDs 24 arranged on the LED boards
25 constituting a single row are connected in series to be turned on or
off altogether by a single control circuit, thus achieving cost
reduction. The LED boards 25 arranged along the Y-axis direction have
substantially the same arrangement pitch. Thus, in the chassis 22, the
LEDs 24 are arranged in a planar manner along the bottom plate 22a in the
chassis 22 at substantially regular intervals with respect to the X-axis
direction and the Y-axis direction.

[0068] The diffuser lenses 27 are made of a substantially transparent
(highly light transmissive) synthetic resin material with a refractive
index higher than that of air (such as polycarbonate or acrylic
material). The diffuser lenses 27 have a predetermined thickness and a
substantially circular shape in plan view, as shown in FIGS. 6 and 7. The
diffuser lenses 27 are attached to the LED boards 25 to cover the LEDs 24
individually from the front side, that is, the diffuser lenses 27 overlap
with the LEDs 24 in plan view. The diffuser lenses 27 are configured to
output the light emitted by the LEDs 24, which has strong directionality,
in a diffusing manner. Specifically, the light emitted by the LEDs 24
passes through the diffuser lenses 27 to reduce its directionality.
Therefore, the regions between the adjacent LEDs 24 can be prevented from
being visually recognized as being dark even when the intervals between
the LEDs 24 are increased. Thus, the number of LEDs 24 installed can be
decreased. The diffuser lenses 27 are substantially coaxial with the LEDs
24 in plan view.

[0069] Next, the holding members 28 will be described. The holding members
28 are made of a synthetic resin, such as polycarbonate resin, and have a
white surface for excellent light reflectivity. The holding member 28, as
shown in FIGS. 6 to 8, includes a main body portion 28a extending along
the plate surface of the LED boards 25, and a fixing portion 28b
protruding from the main body portion 28a toward the rear side, i.e., the
chassis 22, to be fixed to the chassis 22. The main body portion 28a has
a substantially circular plate-like shape in plan view and is configured
to sandwich the LED boards 25 and the reflection sheet 29, which will be
described in detail later, with the bottom plate 22a of the chassis 22.
The fixing portion 28b penetrates through insertion holes 25b and the
attaching holes 22d, which are respectively formed in the LED boards 25
and the bottom plate 22a of the chassis 22 at positions corresponding to
the attaching positions of the holding members 28, to be locked on the
bottom plate 22a. As shown in FIG. 6, a number of the holding members 28
are arranged side by side in rows and columns on the planes of the LED
boards 25. Specifically, the holding members 28 are arranged between the
adjacent diffuser lenses 27 (LEDs 24) with respect to the X-axis
direction.

[0070] Of the holding members 28, a pair arranged at the center of the
screen includes a support portion 28c protruding from the main body
portion 28a toward the front side. The support portion 28c is configured
to support the optical members 23 (or the diffuser plate 23a directly)
from the rear side to maintain a constant positional relationship between
the LEDs 24 and the optical members 23 in the Z-axis direction and
thereby to prevent unexpected deformation of the optical members 23.

[0071] The reflection sheet 29 is made of a synthetic resin and has a
white surface for excellent light reflectivity. The reflection sheet 29,
as shown in FIGS. 6 to 8, is dimensioned to be laid over substantially
the entire area of the inner surface of the chassis 22 to cover all the
LED boards 25 disposed in rows and columns in the chassis 22 at once from
the front side. The reflection sheet 29 is configured to reflect the
light in the chassis 22 toward the optical members 23. The reflection
sheet 29 includes: a bottom portion 29a extending along the bottom plate
22a of the chassis 22 and dimensioned to cover most of the bottom plate
29a; four rising portions 29b rising from the respective outer ends of
the bottom portion 29a toward the front side and inclined with respect to
the bottom portion 29a; and extension portions 29c extending outward from
the outer ends of the rising portions 29b and placed on the backing
plates 22c of the chassis 22. The bottom portion 29a of the reflection
sheet 29 is disposed on the front side surface of the LED boards 25,
i.e., in overlapping manner with respect to the mounting surface for the
LEDs 24 on the front side. The bottom portion 29a of the reflection sheet
29 has lens insertion holes 29d for the diffuser lenses 27 at positions
overlapping with the respective to the diffuser lenses 27 (LEDs 24) in
plan view (as shown in FIGS. 6).

[0072] As described above, according to the present embodiment, the color
filter 19 of the liquid crystal panel 11, as shown in FIGS. 3 and 5,
includes the yellow color section Y in addition to the color sections R,
G, and B of the three primary colors of light. Thus, the color gamut of
the display image displayed by the transmitted light is expanded.
Therefore, the image can be displayed with excellent color
reproducibility. Further, the light transmitted through the yellow color
section Y has wavelength close to the peak of luminosity factor, and
therefore, tends to be perceived by the human eye as being bright even at
small energy level. Thus, sufficient brightness can be obtained even when
the output from the light sources, i.e., the LEDs 24 of the backlight
unit 12 is restrained. Accordingly, the electric power consumption by the
light sources can be decreased and thereby improved environmental
friendliness can be obtained.

[0073] On the other hand, when the four-color liquid crystal panel 11 as
above described is used, the display image of the liquid crystal panel 11
may tend to become yellowish as a whole. In order to avoid this, in the
backlight unit 12 according to the present embodiment, the chromaticity
in the LEDs 24 is adjusted toward blue as the complementary color to
yellow such that the chromaticity in the displayed image can be
corrected. Thus, as described above, the LEDs 24 of the backlight unit 12
have the dominant emission wavelength in the blue wavelength region. The
light in the blue wavelength region has the highest emission intensity.
If the optical members 23 assembled and used in the backlight unit 12 are
continuously irradiated with the light in the blue wavelength region,
i.e., of high emission intensity, the optical characteristics of the
optical members 23 may be changed, and the chromaticity of the color of
white of the transmitted light may be shifted toward blue. When the
chromaticity of the color of white of the transmitted light of the
optical members 23 is changed as above described in association with use
of the backlight unit 12 and the liquid crystal display device 10, the
tinge of the displayed image on the liquid crystal panel 11 may be
gradually changed toward blue with the elapse of the time of use,
possibly resulting in a significant decrease in display quality.
According to the present embodiment, a comparative experiment was
conducted with respect to the prism sheet 23c among the optical members
23 as described below.

[0074] In the comparative experiment, the prism sheet 23c was irradiated
with the light from the LEDs 24 used in the backlight unit 12 for 140
hours, and how the chromaticity of the color of white of the transmitted
light through the prism sheet 23c would change was measured at 20 hour
intervals. The results are shown in FIG. 9. Further, how the chromaticity
of the color of white of the transmitted light through the prism sheet
23c would change, and how the transmittance of the transmitted light at
various wavelengths would change were measured before and after the 100
hours irradiation of the prism sheet 23c with the light from the LEDs 24.
The results are shown in FIGS. 10 and 11. In FIG. 9, the horizontal axis
shows the duration of time of irradiation of the prism sheet 23c with the
light from the LEDs 24 (in units "H"), while the vertical axis shows the
chromaticity of the color of white of the transmitted light using x and y
values. Specifically, in FIG. 9, the solid line indicates the x value of
the chromaticity, and the dashed line indicates the y value of the
chromaticity. The x and y values are the values of the chromaticity
coordinates in the CIE (Commission Internationale de l'Eclairage) 1931
chromaticity diagrams shown in FIG. 10. FIG. 10 is the CIE1931
chromaticity diagram showing the x value on the horizontal axis and the y
value on the vertical axis, where the white circle "◯"
indicates the chromaticity coordinates before irradiation of the prism
sheet 23c with the light from the LEDs 24, while the cross mark "X"
indicates the chromaticity coordinates after the 100 hours irradiation.
The direction of change in the chromaticity coordinates as a result of
irradiation is indicated by the arrow. In FIG. 11, the horizontal axis
shows the wavelength of the transmitted light through the prism sheet 23c
(in units "nm"), and the vertical axis shows the transmittance of the
transmitted light of the prism sheet 23c (in units "%"). Specifically,
FIG. 11 shows the difference in transmittance at each wavelength which
was obtained by subtracting the transmittance of the transmitted light
through the prism sheet 23c prior to irradiation from the transmittance
of the transmitted light through the prism sheet 23c after 100 hours
irradiation. Thus, in FIG. 11, a positive (+) transmittance means that
the transmittance is increased by the 100 hours irradiation, while a
negative transmittance (-) means that the transmittance is decreased by
the irradiation.

[0075] The results of the comparative experiment will be described. It is
seen from the graph of FIG. 9 that, when the prism sheet 23c is
irradiated with the light from the LEDs 24, the x and the y values
indicating the chromaticity of the color of white of the transmitted
light are gradually decreased with the elapse of the time of irradiation.
In the CIE1931 chromaticity diagram shown in FIG. 10, both the x and y
values of the chromaticity of the color of white are decreased, and as a
result, shifted in the direction indicated by the arrow, which means that
the chromaticity of the color of white is shifted toward blue. It is also
seen from the graph of FIG. 9 that after 100 hours irradiation with the
light from the LEDs 24, the change in the chromaticity of the transmitted
light through the prism sheet 23c is very small, converging into a
generally constant value. In other words, as the prism sheet 23c is
irradiated with the light from the LEDs 24, the chromaticity of the color
of white of the transmitted light continues changing toward blue over
time; after about 100 hours, however, the chromaticity is hardly changed
and becomes stable. Specifically, when the difference between the
chromaticity before irradiation with the light from the LEDs 24 and the
chromaticity that is stabilized after 100 hours or more of the
irradiation is expressed by Δx and Δy respectively, Δx
is 0.0143 and Δy is 0.0258.

[0076] Further, it is seen from the graph of FIG. 11 that, except for a
violet wavelength region (380 nm to 435 nm) and a longer wavelength part
of a red wavelength region (750 nm to 780 nm), in a shorter wavelength
part of the red wavelength region (600 nm to 750 nm), a yellow wavelength
region (580 nm to 600 nm), a green wavelength region (500 nm to 560 nm),
and the blue wavelength region (435 nm to 480 nm), the optical
characteristics of the prism sheet 23c are changed such that the
transmittance is generally increased by irradiating the prism sheet 23c
with the light from the LEDs 24. More specifically, in the blue
wavelength region, the transmittance is particularly increased compared
with the transmittance of the other colors (such as red, green, and
yellow). This means that the amount of increase in the transmitted light
in the blue wavelength region is greater than the amount of increase in
the transmitted light in the wavelength region of other colors; namely,
the absorptance with respect to the light of the blue wavelength region
is lower than the absorptance with respect to the light of the wavelength
region of other colors. If the amount of transmitted light in the blue
wavelength region is larger than the amount of transmitted light in the
wavelength region of other colors, the chromaticity of the color of white
of the transmitted light is shifted toward blue, which supports the
result shown in FIG. 10. The chromaticity shift of the transmitted light
is an irreversible change.

[0077] The reasons for the shift in the chromaticity of the color of white
of the transmitted light through the prism sheet 23c toward blue may
include the use environment involving the long-term irradiation with the
light from the LEDs 24 that has high emission intensity in the blue
wavelength region, and the material of the prism sheet 23c, for example.
Specifically, it may be surmised that, because the light in the blue
wavelength region has particularly high optical energy among the visible
rays of light, the light acts on the chromophore (more specifically, the
carbonyl group in PET) included in the light transmissive base member 30
of the prism sheet 23c to change the amount of absorption (or the amount
of transmission) of light of the various wavelengths. In addition, the
prism sheet 23c collect light transmitting therethrough. Therefore, the
change in the chromaticity of the transmitted light through the prism
sheet 23c is relatively conspicuous compared with the other optical
members 23a, 23b. Thus, it is important to solve the problem of
chromaticity shift in the prism sheet 23c for an appropriate displayed
image.

[0078] Thus, according to the present embodiment, the manufacturing step
of the prism sheet 23c includes a step of stabilizing the chromaticity of
the transmitted light toward blue in advance. In the following, a method
of manufacturing the prism sheet 23c will be described in detail. The
prism sheet 23c, as shown in FIG. 12, is manufactured through a step of
forming the light transmissive base member 30; a step (functional layer
forming step) of layering the prism layer 31, which is an optical
functional layer, on the light transmissive base member 30; and the
chromaticity stabilizing step of the transmitted light. In the base
member forming step, PET as raw material for the light transmissive base
member 30 is heated and kneaded, and then extruded by an extruder, which
is not shown. The extruded PET is formed into a uniform thickness by
being sandwiched between rollers. In the prism layer forming step, a
non-halogenated acrylic resin as raw material for the prism layer 31 is
extruded and formed into a flat plate shape in the same manner as in the
base member forming step, and then pressed by a die (not shown) of the
prism shape with respect to the one side surface to form the prisms 31a.
Thereafter, the prism layer 31 is affixed to the light transmissive base
member 30 on the opposite side surface of the prisms 31a by using an
affixing apparatus, which is not shown.

[0079] Then, in the chromaticity stabilizing step, as shown in FIG. 13,
the prism sheet 23c formed through the base member forming step and the
prism layer forming step is irradiated with light from chromaticity
stabilizing LEDs 32, on one of the main plate surfaces, i.e., the front
and rear sides, of the prism sheet 23c. The chromaticity stabilizing LEDs
32 will be described in detail. The chromaticity stabilizing LEDs 32 are
disposed downstream in the affixing apparatus used in the prism layer
forming step, in the prism sheet manufacturing line. The chromaticity
stabilizing LEDs 32 are disposed to face the light transmissive base
member 30 of the prism sheet 23c transported out of the affixing
apparatus. Thus, the light from the chromaticity stabilizing LEDs 32
passes through the light transmissive base member 30 before the prism
layer 31.

[0080] On a board 33, a number of the chromaticity stabilizing LEDs 32 are
surface-mounted in a matrix. Specifically, the chromaticity stabilizing
LEDs 32 include LED chips (LED elements; light emitting elements) of an
InGaN-based material, for example, are sealed with a resin material. The
LED chips of the chromaticity stabilizing LEDs 32 have a single peak
wavelength in a range of 435 nm to 480 nm, i.e., the blue wavelength
region, and emit the single color light of blue. More preferably, the LED
chips of the chromaticity stabilizing LEDs 32 have a dominant emission
wavelength in a range of 440 nm to 460 nm, specifically at 451 nm, for
example, which is the same as the dominant emission wavelength of the LED
chips of the LEDs 24 of the backlight unit 12. However, the chromaticity
stabilizing LEDs 32 do not contain a phosphor as in the LEDs 24 of the
backlight unit 12. Thus, the chromaticity stabilizing LEDs 32 have the
same dominant emission wavelength of the LEDs 24 of the backlight unit 12
and emit the single color light of blue with excellent color purity. The
emission intensity of the light in the blue wavelength region from the
chromaticity stabilizing LEDs 32 is relatively higher than the
corresponding emission intensity from the LEDs 24 of the backlight unit
12.

[0081] In the chromaticity stabilizing step, the prism sheet 23c formed
through the base member forming step and the prism layer forming step is
irradiated with the light from the chromaticity stabilizing LEDs 32 for a
predetermined time such that the chromaticity of the color of white of
the transmitted light can be stabilized. In other words, prior to being
assembled and used in the backlight unit 12, the prism sheet 23c is
stabilized by previously shifting the chromaticity of the color of white
of the transmitted light toward blue such that hardly any more shifting
of the chromaticity is caused. Thus, when the manufactured prism sheet
23c that is subjected to the stabilizing process is assembled and used in
the backlight unit 12, the optical characteristics of the prism sheet 23c
are hardly changed even when the prism sheet 23c is continuously
irradiated with the light from the LEDs 24 of the backlight unit 12.
Therefore, the tinge of the displayed image on the liquid crystal panel
11 is hardly changed over time. Accordingly, high display quality can be
obtained in the liquid crystal display device 10. In addition, the
chromaticity stabilizing LEDs 32 used in the chromaticity stabilizing
step emit the single color light of blue, and have the dominant emission
wavelength in the blue wavelength region. The emission intensity of the
light in the blue wavelength region from the chromaticity stabilizing
LEDs 32 is higher than the emission intensity of the LEDs 24 of the
backlight unit 12. Thus, the chromaticity of the color of white of the
transmitted light through the prism sheet 23c can be stabilized in less
irradiation time than when the LEDs 24 are used (100 hours). In this way,
time required for the chromaticity stabilizing step can be decreased,
leading to high manufacturing efficiency. Further, in the prism sheet 23c
manufactured through the chromaticity stabilizing step, as shown in FIG.
11, the transmittance of the visible rays of light is generally increased
at the various wavelengths (belonging to the shorter wavelength part of
the red wavelength region or the yellow, green, or blue wavelength
region), resulting in an increased brightness of the displayed image.
This means that sufficient brightness in the displayed image can be
obtained even when the output of the LEDs 24 of the backlight unit 12 is
decreased, thereby providing the effect of reduced power consumption.

[0082] As described above, the method of manufacturing the prism sheet 23c
according to the present embodiment, which is used in the backlight unit
12 supplying light to the liquid crystal panel 11 to transmit the light
from the LEDs 24 as light sources of the backlight unit 12, includes the
chromaticity stabilizing step of the transmitted light by irradiation
with the light having the dominant emission wavelength in the blue
wavelength region from the chromaticity stabilizing LEDs 32 as
chromaticity stabilizing light sources.

[0083] When the prism sheet 23c manufactured without the chromaticity
stabilizing step is assembled and used in the backlight unit 12
irradiating the liquid crystal panel 11 with light, the optical
characteristics of the prism sheet 23c would be changed and the
chromaticity of the color of white of the transmitted light would be
gradually shifted toward blue in association with irradiation of the
prism sheet 23c with the light in the blue wavelength region from the
LEDs 24 of the backlight unit 12. As a result, the tinge of the displayed
image would be changed over time, possibly decreasing the display
quality.

[0084] In contrast, according to the present embodiment, the prism sheet
23c is irradiated with the light having the dominant emission wavelength
in the blue wavelength region from the chromaticity stabilizing LEDs 32
to change the optical characteristics of the prism sheet 23c in the
chromaticity stabilizing step during the manufacture of the prism sheet
23c, such that the chromaticity of the transmitted light of the prism
sheet 23c can be shifted toward blue. Namely, a change in the optical
characteristics of the prism sheet 23c to be used in the backlight unit
12 is promoted in advance during the manufacturing process such that the
chromaticity of the color of white of the transmitted light is shifted
toward blue, whereby the chromaticity of the transmitted light can be
stabilized. Thus, when the prism sheet 23c is assembled and used in the
backlight unit 12, a change in the chromaticity is less likely to occur.
Accordingly, when the prism sheet 23c is used in the backlight unit 12,
the tinge of the displayed image on the liquid crystal panel 11 is not
changed over time, and therefore excellent display quality can be
obtained. Because the light from the chromaticity stabilizing LEDs 32 has
the dominant emission wavelength in the blue wavelength region, the
change in the optical characteristics of the prism sheet 23c can be
efficiently promoted, and time required for the chromaticity stabilizing
step can be decreased, whereby high manufacturing efficiency can be
obtained. Thus, according to the present embodiment, the change in the
chromaticity due to use can be made difficult to occur.

[0085] In the chromaticity stabilizing step, the emission intensity of the
light in the blue wavelength region from the chromaticity stabilizing
LEDs 32 is relatively higher than the corresponding emission intensity of
the LEDs 24 of the backlight unit 12. Accordingly, the optical
irradiation time in the chromaticity stabilizing step necessary for
stabilizing the chromaticity of the transmitted light from the prism
sheet 23c can be decreased more as the emission intensity of the light in
the blue wavelength region is increased. Thus, time required for the
chromaticity stabilizing step can be decreased compared with the case
where the same LEDs as the LEDs 24 of the backlight unit 12 are used as
the chromaticity stabilizing LEDs 32.

[0086] In the chromaticity stabilizing step, the dominant emission
wavelength of the chromaticity stabilizing LEDs 32 is the same as the
dominant emission wavelength of the LEDs 24 of the backlight unit 12. In
this way, the optical characteristics of the prism sheet 23c can be more
appropriately changed in the chromaticity stabilizing step. Thus, when
the manufactured prism sheet 23c is assembled and used in the backlight
unit 12, a more appropriate tinge of color of the displayed image on the
liquid crystal panel 11 can be obtained, leading to an extremely high
display quality.

[0087] In the chromaticity stabilizing step, the chromaticity stabilizing
LEDs 32 emit the substantially single color light of blue. In this way,
the prism sheet 23c can be irradiated with the light in the blue
wavelength region extremely efficiently in the chromaticity stabilizing
step. Thus, in the chromaticity stabilizing step, the irradiation time
necessary for stabilizing the chromaticity of the transmitted light in
the prism sheet 23c can be decreased. Accordingly, time required for the
chromaticity stabilizing step can be further decreased.

[0088] In the chromaticity stabilizing step, the chromaticity stabilizing
LEDs 32 having the LED elements emitting the substantially single color
light of blue are included as the chromaticity stabilizing light sources.
In this way, in the chromaticity stabilizing step, the prism sheet 23c is
irradiated with the substantially single color light of blue having
extremely high color purity from the LED elements of the chromaticity
stabilizing LEDs 32. Thus, time required for the chromaticity stabilizing
step can be further decreased.

[0089] In the base member forming step, the light transmissive base member
30 of the prism sheet 23c is formed. In the chromaticity stabilizing
step, at least the light transmissive base member 30 is irradiated with
the light from the chromaticity stabilizing LEDs 32. This is particularly
suitable in the case where the change in the optical characteristics of
the prism sheet 23c is due to the light transmissive base member 30.

[0090] In the base member forming step, the light transmissive base member
30 is formed from a polyester resin. In this way, the chromaticity of the
transmitted light in the light transmissive base member 30 of a polyester
resin can be stabilized through the chromaticity stabilizing step.

[0091] In the base member forming step, the light transmissive base member
30 is formed from PET (polyethylene terephthalate). In this way, although
PET includes a carbonyl group as the chromophore and the carbonyl group
may be a factor causing a change in the optical characteristics, the
chromaticity of the transmitted light from the light transmissive base
member 30 of PET can be stabilized through the chromaticity stabilizing
step.

[0092] In the prism layer forming step (functional layer forming step),
the prism layer 31, which is an optical functional layer providing the
transmitted light with an optical effect, is layered on the light
transmissive base member 30. In this way, the prism sheet 23c including
the prism layer 31 layered on the light transmissive base member 30 can
be manufactured in a preferred manner.

[0093] The chromaticity stabilizing step follows the base member forming
step and the prism layer forming step. If the base member forming step
and the prism layer forming step are performed successively, performing
the chromaticity stabilizing step prior to the prism layer forming step
would require a significant modification of the manufacturing apparatus.
In this respect, according to the present embodiment, the chromaticity
stabilizing step can be included in the method of manufacturing the prism
sheet 23c without any significant modification of the manufacturing
apparatus.

[0094] In the chromaticity stabilizing step, the chromaticity stabilizing
LEDs 32 are disposed in an opposed manner with respect to at least the
light transmissive base member 30. In this way, the light transmissive
base member 30 can be efficiently irradiated with the light from the
chromaticity stabilizing LEDs 32 in the chromaticity stabilizing step.
Thus, the chromaticity of the transmitted light through the light
transmissive base member 30 can be stabilized in less time.

[0095] In the chromaticity stabilizing step, the chromaticity stabilizing
LEDs 32 may be disposed in an opposed manner with respect to the light
transmissive base member 30 among the light transmissive base member 30
and the prism layer 31. In this way, because the chromaticity stabilizing
LEDs 32 are disposed in an opposed manner with respect to only one side
of the prism sheet 23c, the cost associated with a manufacturing
apparatus for the prism sheet 23c can be decreased compared with the case
where the chromaticity stabilizing LEDs 32 are disposed in an opposed
manner with respect to both sides of the prism sheet 23c.

[0096] The optical functional layer is the prism layer 31 that collects
light transmitting therethrough. In this way, in the prism sheet 23c
including the prism layer 31, because the transmitted light is collected
by the prism sheet 23c, the chromaticity shift of the color of white of
the transmitted light toward blue tends to become more conspicuous. In
this respect, according to the present embodiment, the chromaticity of
the transmitted light from the prism sheet 23c is stabilized in advance
in the chromaticity stabilizing step, which is extremely useful in the
manufacture of the prism sheet 23c including the prism layer 31.

[0097] The prism layer 31 is made of a non-halogenated acrylic resin. In
this way, the prism sheet 23c including the prism layer 31 of a
non-halogenated acrylic resin can be manufactured in an extremely useful
manner.

[0098] In the chromaticity stabilizing step, the prism sheet 23c to be
used in the backlight unit 12 is irradiated with the light from the
chromaticity stabilizing LEDs 32. In the backlight unit 12, the light
sources are the LEDs 24 including the LED elements emitting the
substantially single color light of blue and the phosphor emitting light
upon excitation by the light from the LED elements. If the prism sheet
23c is used in the backlight unit 12 including the LEDs 24 as the light
sources, the problem of the chromaticity shift of the transmitted light
as a result of the change in the optical characteristics of the prism
sheet 23c may become pronounced due to the substantially single color
light of blue with extremely high color purity from the LED elements.
Thus, by stabilizing the chromaticity of the transmitted light with
respect to the prism sheet 23c used in the backlight unit in the
chromaticity stabilizing step, the problem of chromaticity shift can be
eliminated in a preferred manner.

[0099] In the chromaticity stabilizing step, the prism sheet 23c to be
used in the backlight unit 12 is irradiated with the light from the
chromaticity stabilizing LEDs 32. The backlight unit 12 supplies light to
the liquid crystal panel 11, in which a substance with optical
characteristics variable by application of an electric field is provided
between the pair substrates 11a, 11b, and the color filter 19 including a
plurality of color sections R, G, B, or Y exhibiting blue, green, red,
and yellow, respectively, is formed on one of the pair of substrates 11a,
11b. Because the color filter 19 included in the liquid crystal panel 11
includes the yellow color section Y in addition to the blue, green, and
red color sections R, G, and B, the displayed image on the liquid crystal
panel 11 tends to have a yellowish tinge. In order to avoid this, the
chromaticity of the output light of the LEDs 24 of the backlight unit 12
may preferably be set toward blue, which is the complementary color to
yellow. However, in this case, the problem of the chromaticity shift of
the transmitted light through the prism sheet 23c may become pronounced
when the backlight unit 12 is used. This problem of the chromaticity
shift can be eliminated in a preferred manner by stabilizing the
chromaticity of the transmitted light through the prism sheet 23c used in
the backlight unit 12 supplying light to the liquid crystal panel 11 in
the chromaticity stabilizing step.

Second Embodiment

[0100] A second embodiment of the present invention will be described with
reference to FIGS. 14 and 15. In the second embodiment, the diffuser
sheet 23b of the optical members 23 is manufactured through a step of
stabilizing chromaticity. Redundant description of structures,
operations, and effects similar to those of the first embodiment will be
omitted.

[0101] Of the optical members 23, the diffuser sheet 23b as well as the
prism sheet 23c may also be subjected to the chromaticity shift of the
color of white of the transmitted light toward blue when the diffuser
sheet 23b is assembled and used in the backlight unit 12. In this case,
it is preferable to include a step of stabilizing chromaticity also in
steps of manufacturing the diffuser sheet 23b. In the following, a
structure of the diffuser sheet 23b and a method of manufacturing the
same will be described in detail.

[0102] The diffuser sheet 23b, as shown in FIG. 14, includes a light
transmissive base member 34 having excellent transmissivity, and a
diffuser layer (optical functional layer) 35 layered on a main plate
surface of the light transmissive base member 34. The diffuser sheet 23b
is configured to provide the transmitted light with a diffusing effect.
The diffuser layer 35 is disposed on the front side (light output side)
with respect to the light transmissive base member 34. The light
transmissive base member 34 is disposed on the rear side (opposite to the
light output side) with respect to the diffuser layer 35. The light
transmissive base member 34 is substantially transparent and has a
horizontally long sheet shape, with a generally smooth surface. On the
other hand, the diffuser layer 35 contains a number of spherical
diffusing beads 35a disposed on the surface of the light transmissive
base member in a dispersed manner. The light passing through the diffuser
sheet 23b is irregularly reflected by the diffusing beads 35a of the
diffuser layer 35 to lose directionality and be diffused. The light
transmissive base member 34 may be made of an AS resin
(acrylonitrile-styrene copolymer). The diffuser layer 35 may be made of
an alkyl methacrylate styrene non-copolymer.

[0103] The diffuser sheet 23b of the above configuration may be
manufactured through a step of forming the light transmissive base member
34; a step (functional layer forming step) of layering the diffuser layer
35, which is an optical functional layer, on the light transmissive base
member 34; and a step of stabilizing the chromaticity of the transmitted
light. The base member forming step may be the same step for the prism
sheet 23c according to the first embodiment. In the diffuser layer
forming step, the diffuser layer 35 is formed by applying a diffusing
agent containing a number of diffusing beads 35a dispersed in a
predetermined solution onto the surface of the light transmissive base
member 34 to have a generally uniform thickness. In the chromaticity
stabilizing step, as shown in FIG. 15, the diffuser sheet 23b formed
through the base member forming step and the diffuser layer forming step
is irradiated with the light from the chromaticity stabilizing LEDs 32 on
the side of the light transmissive base member 34. The chromaticity
stabilizing LEDs 32 may be similar to those shown according to the first
embodiment; thus, redundant description will be omitted.

[0104] The diffuser sheet 23b manufactured by the above manufacturing
method is stabilized prior to being assembled and used in the backlight
unit 12 such that the chromaticity of the color of white of the
transmitted light is shifted toward blue in advance and made to be hardly
changed any further. Thus, even when the manufactured diffuser sheet 23b
is assembled and used in the backlight unit 12 and irradiated with the
light from the LEDs 24 of the backlight unit 12 continuously, the optical
characteristics of the diffuser sheet 23b are hardly changed. Thus, the
tinge of the displayed image on the liquid crystal panel 11 is hardly
changed over time. Accordingly, high display quality of the liquid
crystal display device 10 can be obtained.

[0105] As described above, according to the present embodiment, the
optical functional layer formed on the light transmissive base member 34
in the functional layer forming step is the diffuser layer 35 providing
the transmitted light with a diffusing effect. In this way, the diffuser
sheet 23b including the diffuser layer 35 providing the transmitted light
with a diffusing effect can be manufactured in a preferred manner.

[0106] In the base member forming step, the light transmissive base member
34 is formed from an AS resin (acrylonitrile-styrene copolymer). In this
way, the chromaticity of the transmitted light through the light
transmissive base member 34 of the AS resin can be stabilized through the
chromaticity stabilizing step.

[0107] The diffuser layer 35 is made of an alkyl methacrylate styrene
non-copolymer. In this way, the diffuser sheet 23b including the diffuser
layer 35 of the alkyl methacrylate styrene non-copolymer can be
manufactured in a preferred manner.

Third Embodiment

[0108] A third embodiment of the present invention will be described with
reference to FIGS. 16 to 19. In the third embodiment, an edge light
backlight unit 212 including a diffusing member 223 will be described.
Redundant description of structures, operations, and effects similar to
those of the first embodiment will be omitted.

[0109] A liquid crystal display device 210 according to the present
embodiment, as shown in FIG. 16, includes a liquid crystal panel 211 and
the edge light backlight unit 212 in an integrated manner using a bezel
213 or the like. The configuration of the liquid crystal panel 211 may be
similar to the first embodiment and redundant description will be
omitted. In the following, the configuration of the edge light backlight
unit 212 will be described.

[0110] The backlight unit 212, as shown in FIG. 16, includes a
substantially box-shaped chassis 222 with an opening on the light output
surface side (the side facing the liquid crystal panel 211); and a
plurality of optical members 223 covering the opening of the chassis 222.
The chassis 222 houses LEDs (Light Emitting Diodes) 224 as light sources;
LED boards 225 on which the LEDs 224 are mounted; a light guide member 36
that guides the light from the LEDs 224 toward the optical members 223
(the liquid crystal panel 211); and a frame 226 retaining the light guide
member 36 from the front side. Each one of the LED boards 225 with the
LEDs 224 is arranged at both ends of the backlight unit 212 on the long
sides thereof with the light guide member 36 sandwiched between the LED
boards 225 at the center. Thus, the backlight unit 212 is of the
so-called edge light type (side light type). The backlight unit 212
according to the present embodiment, which is of the edge light type,
does not include the diffuser lenses 27, the holding members 28, the
first reflection sheet 30, the second reflection sheets 31, or the like
included in the direct backlight unit 12 according to the first
embodiment. In the following, the constituent components of the backlight
unit 212 will be described in detail.

[0111] The chassis 222 is made of metal and, as shown in FIGS. 17 and 18,
includes a bottom plate 222a with a horizontally long square shape
similar to the liquid crystal panel 211, and side plates 222b rising from
the outer ends of the sides of the bottom plate 222a. Thus, the chassis
222 as a whole has a shallow, substantially box-like shape with an
opening on the front side. The chassis 222 (bottom plate 222a) has a long
side direction aligned with the X-axis direction (horizontal direction)
and a short side direction aligned with the Y-axis direction (vertical
direction). To the side plates 222b, the frame 226 and the bezel 213 can
be threadably attached.

[0112] The optical members 223, as shown in FIG. 16, include a diffuser
plate 223a disposed on the rear side (the side of the LEDS 224; opposite
to the light output side), and optical sheets 223b to 223d disposed on
the front side (the side of the liquid crystal panel 211; the light
output side). The diffuser plate 223a is similar to the diffuser plate
according to the first embodiment; thus, redundant description will be
omitted. The optical sheets 223b to 223d are layered in the order of the
diffuser sheet 223b, the reflection type polarizing sheet 223d, and the
prism sheet 223c from the rear side (the side of the diffuser plate
223a). With regard to the diffuser sheet 223b and the prism sheet 223c,
the chromaticity of the color of white of the transmitted light may be
stabilized by including the chromaticity stabilizing step in the
manufacturing method as described above with reference to the first
embodiment and the second embodiment, before the diffuser sheet 223b or
the prism sheet 223c is assembled and used in the backlight unit 212.
Also with regard to the reflection type polarizing sheet 223d, a step of
stabilizing chromaticity may be included in the manufacturing method as
in the case of the diffuser sheet 223b and the prism sheet 223c.

[0113] The frame 226 has a frame-like shape extending along the outer
peripheral ends of the light guide member 36 to retain substantially the
entire peripheral ends of the light guide member 36 from the front side.
The frame 226 is made of a synthetic resin and has a black surface, for
example, providing light blocking property. On the rear side surfaces of
both the long side portions of the frame 226, which faces the light guide
member 36 and the LED boards 225 (LEDs 224), each one of first reflection
sheets 37 reflecting light are attached, as shown in FIG. 17. The first
reflection sheets 37 are sized to extend along substantially the entire
length of the long side portions of the frame 226. In addition, the first
reflection sheets 37 are directly abutted on the end portions of the
light guide member 36 on the LED 224 side. Thus, the first reflection
sheets 37 cover both the end portions of the light guide member 36 and
the LED boards 225 altogether from the front side. The frame 226 is
configured to receive the outer peripheral end portions of the liquid
crystal panel 211 from the rear side.

[0114] The LEDs 224 are mounted on the LED boards 225, as shown in FIG. 16
with the light emitting surface on the opposite side of the LED-mounting
surface, that is the so-called top type. On the light emitting surface
side of the LEDs 224, lens members 38 outputting light while diffusing it
at large angles are provided, as shown in FIGS. 17 and 19. The lens
members 38 are interposed between the LEDs 24 and light incident surfaces
36b of the light guide member 36. The lens members 38 have a spherical
light output surface to be convex toward the light guide member 36. The
light output surface of the lens members 38 is curved along the length
direction of the light incident surfaces 36b of the light guide member 36
to have a substantially circular cross section. The configuration of the
LEDs 224 may be similar to the first embodiment and redundant description
will be omitted.

[0115] The LED boards 225, as shown in FIG. 16, have a thin plate-like
shape extending along the long side direction (the X-axis direction; the
longitudinal direction of the light incident surfaces 36b of the light
guide member 36) of the chassis 222, with main plate surfaces parallel
with the X-axis direction and the Z-axis direction. Specifically, the LED
boards 225 are housed in the chassis 222 with their plate surfaces
orthogonal to the plate surfaces of the liquid crystal panel 211 and the
light guide member 36 (the optical members 223). The LED boards 225 are
arranged as a pair, one at each end of the chassis 222 on the long side
thereof, respectively to be attached to the inner surfaces of the side
plates 222b on the long side. The LEDs 224 are surface-mounted on the
main plate surfaces or the inner side of the LED boards 225, i.e., the
surface facing the light guide member 36. Specifically, a plurality of
the LEDs 224 is arranged side by side in a line on the mounting surface
of the LED boards 225 along the length direction thereof (X-axis
direction). In other words, a plurality of the LEDs 224 is arranged side
by side on each of the end portions of the backlight unit 212 on the long
sides along the long side direction. Because the pair of the LED boards
225 is housed in the chassis 222 with the mounting surfaces for the LEDs
224 opposed to each other, the light emitting surfaces of the LEDs 224
mounted on the LED boards 225 are opposed to each other, with the optical
axes of the LEDs 224 substantially aligned with the Y-axis direction.

[0116] The base member of the LED boards 225 may be made of the same metal
material as the chassis 222, such as aluminum based material. On the
surface of the base member, a wiring pattern (not shown) of a metal film,
such as copper foil, is formed via an insulating layer. On the outer-most
surface of the base member, a white reflective layer (not shown) with
excellent light reflectivity is formed. The LEDs 224 arranged side by
side in a line on the LED boards 225 are connected in series by the
wiring pattern. As the material of the base member of the LED boards 225,
an insulating material, such as ceramic material, may be used.

[0117] The light guide member 36 will be described in detail. The light
guide member 36 is made of a substantially transparent (highly light
transmissive) synthetic resin material (such as acrylic) with a
refractive index sufficiently higher than that of air. The light guide
member 36, as shown in FIG. 16, has a horizontally long square shape in
plan view similar to the liquid crystal panel 211 and the chassis 222,
with the long side direction aligned with the X-axis direction and the
short side direction aligned with the Y-axis direction. The light guide
member 36 is arranged immediately under the liquid crystal panel 211 and
the optical members 223 in the chassis 222 in a sandwiching manner with
respect to the Y-axis direction between the pair of LED boards 225
arranged at the ends of the chassis 222 on the long sides. Thus, the
arrangement direction of the LEDs 224 (LED boards 225) and the light
guide member 36 is aligned with the Y-axis direction, while the
arrangement of the optical members 223 (the liquid crystal panel 211) and
the light guide member 36 is aligned with the Z-axis direction, the
directions of both arrangement being orthogonal to each other. The light
guide member 36 has the function of making the light emitted by the LEDs
224 in the Y-axis direction incident thereon and directing the light
upward to output toward the optical members 223 (the Z-axis direction)
while allowing the light to travel within the light guide member 36. The
light guide member 36 is a little larger than the optical members 223
such that the outer peripheral end portions of the light guide member 36
extend outward beyond the outer peripheral end surfaces of the optical
members 223, where is retained by the frame 226 (FIGS. 17 and 18).

[0118] The light guide member 36 has a substantially flat plate-like
shape, which extends along the plate surfaces of the bottom plate 222a of
the chassis 222 and the optical members 223, with main plate surfaces
parallel with the X-axis direction and the Y-axis direction. The
front-side one of the main plate surfaces of the light guide member 36
constitutes a light output surface 36a, from which the internal light is
output toward the optical members 223 and the liquid crystal panel 211.
Of the outer peripheral end surfaces adjacent to the main plate surfaces
of the light guide member 36, the elongated end surfaces on the long
sides extending along the X-axis direction are opposite to the LEDs 224
(the LED boards 225) with a predetermined interval therebetween; namely,
the longitudinal end surfaces constitute light incident surfaces 36b, on
which the light emitted by the LEDs 224 is incident. The light incident
surfaces 36b are parallel to the X-axis direction and the Z-axis
direction and substantially orthogonal to the light output surface 36a.
The arrangement direction of the LEDs 224 and the light incident surfaces
36b is aligned with the Y-axis direction and parallel to the light output
surface 36a. The light guide member 36 has a surface 36c opposite to the
light output surface 36a, which is entirely covered with a second
reflection sheet 39 reflecting the light within the light guide member 36
upward toward the front side. The second reflection sheet 39 extends to
areas overlapping with the LED boards 225 (LEDs 224) in plan view to
sandwich the LED boards 225 (LEDs 224) with the first reflection sheets
37 on the front side. Thus, the light from the LEDs 224 is repeatedly
reflected between the reflection sheets 37 and 39, thereby causing the
light to be incident on the light incident surfaces 36b efficiently. At
least one of the light output surface 36a and the opposite surface 36c of
the light guide member 36 is patterned with a reflecting portion (not
shown) reflecting the internal light or a scattering portion (not shown)
scattering the internal light, and thereby the output light from the
light output surface 36a is controlled to have a uniform in-plane
distribution.

[0119] By including the chromaticity stabilizing step in the method of
manufacturing the optical members 223 used in the edge light backlight
unit 212, the display quality of the liquid crystal panel 211 can be
increased as in the case of the first embodiment.

Fourth Embodiment

[0120] A fourth embodiment of the present invention will be described with
reference to FIG. 20 or 21. In the fourth embodiment, a color filter 319
of a liquid crystal panel 311 has three colors. Redundant description of
structures, operations, and effects similar to those of the first
embodiment will be omitted.

[0121] As shown in FIGS. 20 and 21, a CF substrate 311a of the liquid
crystal panel 311 according to the present embodiment is provided with
the color filter 319 including a number of color sections R, G, or B
arranged in a matrix corresponding to the pixels on the side of an array
substrate 311b. The color filter 319 includes three kinds of color
sections; namely, the red color section R; the green color section G; and
the blue color section B, corresponding to the three primary colors of
light. In the color filter 319, the color sections are arranged in the
order of the red color section R, the green color section G, and the blue
color section B repeatedly from the left of FIG. 20 along the X-axis
direction. The color sections R, G, and B have a vertically long
(elongated) square (rectangular) shape with a long side direction aligned
with the Y-axis direction and a short side direction aligned with the
X-axis direction, and have the same area for all of the colors. Between
the color sections R, G, and B, a lattice-shaped light blocking layer
(black matrix) BM preventing the mixing of colors is provided. In other
respects, the present embodiment is similar to the first embodiment;
thus, redundant description will be omitted. By including a step of
stabilizing chromaticity in the method of manufacturing the optical
members 23 to be used in the backlight unit 12 to be assembled onto the
back surface of the liquid crystal panel 311 of the three primary color
type, the display quality of the liquid crystal panel 311 can be
increased as in the first embodiment.

Other Embodiments

[0122] The present invention is not limited to the embodiments above
described and illustrated with reference to the drawings, and the
following embodiments may be included in the technical scope of the
present invention.

[0123] (1) The order of arrangement of the color sections in the color
filter of the liquid crystal panel of four original color type may be
appropriately modified, other than that according to the first
embodiment. For example, as shown in FIG. 22, the present invention
includes a configuration in which the color sections R, G, B, and Y in a
color filter 19' are arranged in the order of the red color section R,
the green color section G, the blue color section B, and the yellow color
section Y from the left of the figure along the X-axis direction. The
order of arrangement of the color sections R, G, and B of the liquid
crystal panel of the three primary color type according to the fourth
embodiment may also be modified.

[0124] (2) Other than (1), the present invention includes a configuration
in which, as shown in FIG. 23, the color sections R, G, B, and Y in a
color filter 19'' are arranged in the order of the red color section R,
the yellow color section Y, the green color section G, and the blue color
section B from the left of the figure along the X-axis direction.

[0125] (3) In the method of manufacturing an optical member according to
the foregoing embodiments, the chromaticity stabilizing step is performed
after the base member forming step and the functional layer forming step.
However, the order of performing the steps may be modified such that, for
example, the functional layer forming step is performed after the base
member forming step and the chromaticity stabilizing step. Namely, the
light transmissive base member is formed first, and then, prior to
forming the optical functional layer, only the light transmissive base
member is irradiated with the light from the chromaticity stabilizing
light source.

[0126] (4) In the foregoing embodiments, the chromaticity stabilizing LEDs
are opposite to the light transmissive base member among the optical
members in the chromaticity stabilizing step. However, the present
invention may include a configuration in which the chromaticity
stabilizing LEDs are opposite to the optical functional layer among the
optical members.

[0127] (5) In the foregoing embodiments, the chromaticity stabilizing LEDs
are opposite to only one side of the optical members in the chromaticity
stabilizing step. However, the present invention may include a
configuration in which a pair of the chromaticity stabilizing LEDs is
disposed on both sides of the optical members.

[0128] (6) In the foregoing embodiments, the chromaticity stabilizing LEDs
used in the chromaticity stabilizing step have the same dominant emission
wavelength of the LEDs of the backlight unit. However, the present
invention may also include a configuration in which the dominant emission
wavelength of the chromaticity stabilizing LEDs is made different from
the dominant emission wavelength of the LEDs of the backlight unit (other
than 451 nm in a range of 435 nm to 480 nm). Also in this case, the
dominant emission wavelength of the chromaticity stabilizing LEDs may be
selected preferably from a range of 440 nm to 460 nm.

[0129] (7) Conversely from the above (6), the dominant emission wavelength
of the LEDs of the backlight unit may be made different from the dominant
emission wavelength of the chromaticity stabilizing LEDs.

[0130] (8) In the foregoing embodiments, the chromaticity stabilizing LEDs
are used as the chromaticity stabilizing light sources in the
chromaticity stabilizing step. However, the present invention may also
include a configuration in which other types of light source (such as a
xenon lamp) are used as the chromaticity stabilizing light sources.

[0131] (9) In the foregoing embodiments, the chromaticity stabilizing LEDs
used in the chromaticity stabilizing step emit the single color light of
blue. However, with respect to the chromaticity stabilizing LEDs, it is
also possible to use LEDs that have a plurality of peak wavelengths in
the blue wavelength region, or LEDs that have a peak wavelength in a
wavelength region other than and in addition to the blue wavelength
region. In other words, some of the light emitted by the chromaticity
stabilizing LEDs may belong to a wavelength region other than the blue
wavelength region as long as the light has the dominant emission
wavelength in the blue wavelength region; namely, as long as the light
has the highest emission intensity in the blue wavelength region.

[0132] (10) In the foregoing embodiments, the emission intensity of the
light in the blue wavelength region from the chromaticity stabilizing
LEDs used in the chromaticity stabilizing step is relatively higher than
the corresponding emission intensity of the LEDs of the backlight unit.
However, the chromaticity stabilizing LEDs and the LEDs of the backlight
unit may have the same emission intensity.

[0133] (11) In the first embodiment, the light transmissive base member
and the prism layer of the prism sheet are made of different materials.
However, the light transmissive base member and the prism layer may be
made of the same material. In this case, in the prism layer forming step,
the prism layer is formed by pressing a die of a prism shape directly
onto the surface of the light transmissive base member obtained through
the base member forming step.

[0134] (12) The material of the light transmissive base member of the
prism sheet may be modified as appropriate. For example, the material may
be the same AS resin as the diffuser sheet. Alternatively, an acrylic
resin, PS (polystyrene), or PP (polypropylene) may be used. Similarly,
the material of the prism layer may be modified as appropriate.

[0135] (13) In the second embodiment, the diffuser layer is formed by
applying the diffusing agent onto the surface of the light transmissive
base member of the diffuser sheet. Alternatively, the diffuser sheet may
be manufactured by initially forming a diffuser layer on a surface of a
transparent film separate from the light transmissive base member, and
then affixing the film onto the light transmissive base member.

[0136] (14) Other than the above (13), the diffuser sheet may be
manufactured by mixing diffusing beads in the light transmissive base
member in a dispersed manner.

[0137] (15) The material of the light transmissive base member of the
diffuser sheet may be modified as appropriate. For example, the material
may be the same polyester resin (such as PET) as the prism sheet.
Alternatively, an acrylic resin, PS (polystyrene), or PP (polypropylene)
maybe used. Similarly, the material of the diffuser layer may be modified
as appropriate.

[0138] (16) In the foregoing embodiments, the chromaticity stabilizing
step is included in the method of manufacturing the optical sheets of the
optical members. Alternatively, the chromaticity stabilizing step may be
included in the method of manufacturing a diffuser plate or a light guide
member, and such a configuration is also included in the present
invention. Also in this case, particularly high effect can be obtained
when the material of the optical members is polyester resin (such as
PET).

[0139] (17) In the first embodiment, the optical sheets used in the direct
backlight unit include two sheets, i.e., the diffuser sheet and the prism
sheet. It is of course possible to include three optical sheets by adding
a reflection type polarizing sheet, or four or more optical sheets by
adding other types of optical sheets. It is also possible to use a
plurality of optical sheets of the same type, such as two diffuser
sheets.

[0140] (18) In the third embodiment, three optical sheets are used in the
edge light backlight unit, i.e., the diffuser sheet, the prism sheet, and
the reflection type polarizing sheet. It is also possible to use four or
more optical sheets by adding other types of optical sheets, or,
conversely, use two or less optical sheets by omitting any of the above
optical sheets. It is also possible to use a plurality of optical sheets
of the same type, such as two diffuser sheets.

[0141] (19) In the first embodiment, the diffuser lens is disposed on the
light output side of the LEDs. However, the present invention may be
applied to a direct backlight unit without such diffuser lens.

[0142] (20) In the foregoing embodiments, the liquid crystal panel and the
chassis are vertically arranged with their short side directions aligned
with the vertical direction, by way of example. The present invention
also includes a configuration in which the liquid crystal panel and the
chassis are vertically arranged with their long side directions aligned
with the vertical direction.

[0143] (21) In the foregoing embodiments, as the switching elements of the
liquid crystal display device, TFTs are used. The present invention,
however, may be applied to liquid crystal display devices using switching
elements other than TFTs (such as thin-film diodes (TFDs)). Further, the
present invention may be applied not only to a liquid crystal display
device for color display but also to a liquid crystal display device for
monochrome display.

[0144] (22) While in the foregoing embodiments liquid crystal display
devices using a liquid crystal panel as a display panel has been
described by way of example, the present invention may be applied to
display devices using other types of display panels.

[0145] (23) While in the foregoing embodiments a television receiver with
a tuner has been described by way of example, the present invention may
be applied to a display device without a tuner.